[Android Compile Server] Check the branch of the specified Gerrit issue
[Android Compile Server] Check the branch of the specified Gerrit issue

isAncestor("HEAD", "origin/master") does not work for Gerrit patches


Bug: skia:7615
Change-Id: I1718de822939c96365b9ee5abc57eb0c92a05f54
Reviewed-on: https://skia-review.googlesource.com/107001
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot